In data storage devices such as disc drives, data is read from a disc by a read operation that involves a mechanical scanning motion of a disc moving relative to a read head. The read data is initially in synchronization with the mechanical motion during writing and needs to be resynchronized as the data is read processed by a computer. This process of resynchronization is accomplished by a timing recovery circuit.
In some disc drives, there is an array of multiple read heads that are reading data simultaneously (i.e., in parallel) on multiple read channels. Each of the multiple channels includes a timing recovery circuit. As the number of parallel channels increases in newer, larger disc drives, the signal-to-noise ratios (SNR's) are degraded, and the multiple timing recovery circuits consume increasing amounts of electrical power and circuit resources in the disc drive. Furthermore, one or more of the timing recovery circuits may not gain synchronization at all due to the degradation of SNR.
The read/write channel of a disc drive is just one example of a general problem of communication channels with increasing numbers of parallel data channels that require timing recovery, but that are increasingly consuming excess electrical power and computing resources to perform timing recovery functions in a receiver portion of the communication channel.
A method and apparatus are needed to provide timing recovery in communication channels that include multiple parallel channels without excess consumption of electrical power and circuit resources in performing the timing recovery. Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.